Molecularly engineered graphene surfaces for sensing applications: A review

Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis.     

Deposition of Titania Nanoparticles on Spherical Silica

Titania coated silica nanoparticles were prepared through a sol-gel process using peptized TiO₂ nano-sols. The TiO₂ sols were obtained by peptization, the process of redispersing a coagulated colloid, and were coated on SiO₂ particles by the control of the weight ratio of TiO₂/SiO₂ and the pH of the mixture in aqueous solution. At pH 4.5 the difference of zeta-potential between SiO₂ and TiO₂ maximized and then the TiO₂-coated SiO₂ particles with highest TiO₂ contents (20%) were obtained without the self-aggregation of TiO₂ sols. The morphologies of particles were characterized with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) and the isoelectric points (IEP) of particles were measured by zeta potential. The nature of exposed titanium ions on the surface of titania-coated silica nanoparticles was elucidated by X-ray photoelectron spectroscopy (XPS).     

Properties of amphoteric polyurethane waterborne dispersions. III. Isoelectric points and precipitation

The isoelectric points of amphoteric polyurethane (APU) with hydrophobic soft segments and pendent ? COOH and ? CH₂N(CH₃)₂ groups and the effect of inorganic salts on the isoelectric points were investigated by the conductivity titration method. The pH values at isoelectric points agreed with the theoretical isoelectric point equations of Patrickios and Merle with pK_a = 6.1 and pK_b = 8.3, even though, as an ionomer, APU has a low density of ionizable groups on the macromolecular chains and takes a micellar state in aqueous media. The precipitation of APU waterborne dispersions also was observed around the isoelectric points and around lower or higher pH values with the ultraviolet spectrophotometric method. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2440–2448, 2002     

酸预处理对酶法骨明胶功能性质和分子质量分布的影响

本文以牛骨粉为原料,采用酶解法制备明胶,考察了骨粉预处理试剂——盐酸的浓度对明胶产品的冻力、粘度、分子量分布和等电点的影响.研究表明,随着骨粉预处理用的盐酸浓度的增大,明胶产率降低.骨粉经过盐酸预处理后,明胶产品的冻力大于300 bloom g,高于原料未经盐酸处理得到的明胶产品.与传统的碱法工艺明胶相比,酶法明胶具有高冻力、高等电点和相对较低的粘度等特点.采用聚丙烯酰胺凝胶电泳表征明胶的分子质量分布,酶法明胶不但具有传统碱法明胶具有的96 KDa、97 KDa、193 KDa和289 KDa组分,而且具有165 KDa和120 KDa组分.酶法明胶的等电点在碱性范围内,随着预处理用盐酸浓度的增大,明胶产品的等电点升高.骨料的预处理工艺对明胶的产率、冻力、粘度、等电点和分子质量分布有重要的影响,在明胶制备过程中,通过调控骨料预处理酸浓度可以调控明胶的技术指标.     

Influence of long-term aqueous exposure on surface properties of plasma sprayed oxides Al2O3, TiO2 and their mixture Al2O3-13TiO2

The surface properties of plasma sprayed Al₂O₃- and TiO₂-based coating materials were characterized in order to investigate the influence of surface strain and phase inhomogenity. The materials were water exposed up to 8 months. The bulk crystallographic structure, dissolution behaviour, effective charge (zeta potential, isoelectric point), surface compositions and oxidation states were determined. In addition, the properties of the aging solutions, such as conductivity, supernatant pH (point of zero charge), and redox potential, were monitored during aging.It was shown that the materials were stable under aging conditions, but that considerable surface rearrangements, such as dissolution-reprecipitation and surface site redistributions may occur. However, overall only minor changes in surface properties results from this restructuring process.